The present invention relates to a navigation device for performing enlarged display of an intersection.
The present invention also relates to a navigation device for performing guidance of a route.
The present invention also relates to a navigation device capable of reproduction through selection from a plurality of storage media which store map information.
It is important for a navigation system mounted on a vehicle to provide information about intersections. As one of the methods of providing this information, enlarged display of an area near the intersection (fork) a vehicle is approaching is disclosed in Japanese Unexamined Patent Publication 4-127015.
In this method of performing enlarged display of the intersection, when a vheicle approaches to within a predetermined distance of the intersection, the enlarged display of the intersection is initiated, and when the vehicle moves away from the intersection, the enlarged display is terminated.
However, when a current position detector position measurement errors, the enlarged display may intermittently appear and disappear while a vehicle is making a temporary stop near a boundary at which the enlarged display of the intersection is to be initiated. In the case of GPS position detector by which radio waves are received from the GPS (Global Positioning System) satellites, the error in the position measurement may lead to an error in the speed measurement of substantially two kilo meters per hour at the maximum. For this reason, when a vehicle makes a temporary stop due to a traffic jam near a boundary at which the enlarged display is to be initiated, the enlarged display may intermittently appear and disappear. This is not satisfactory.
Further, when there is the error in the position measurement, even while the vehicle is making a stop at the intersection, erroneous determination that the vehicle is moving away is sometimes made. It sometimes happens, for example, when an enlarged view of an intersection is not provided while waiting for the traffic lights to change.
Moreover, the enlarged display of an intersection (giving details of the intersection) is carried out automatically with the movement of the vehicle, and the information is not obtained readily when the user desires it at other times.
Another navigation device disclosed in Japanese Utility Model Kokal Publication 5-84975 has a route guidance function. The user sets a planned route by entering a starting point, a destination, and one ore more points on the route as required prior to the actual travel, and display of the set route, guidance for turning by voice, and the like are performed during the actual travel. In addition, recognition or examination of the route by means of simulation can also be performed.
Another navigation device disclosed in Japanese Patent Kokai Publication 5-53500 combines the function of enlarged display of an area near an intersection (fork) with the function of route guidance.
However, there are places where classification of road changes. In Japan, for example, the roads are classified into eight classifications, namely: automotive expressways, metropolitan expressways, national highways, principal local roads, prefectural roads, standard roads having a width of 5.5 m or more, other roads (narrow roads), and ferry routes. The place where this classification of roads changes may be a boundary of prefectures or cities, a boundary at which the restrictions of the road traffic law such as one on speed limits change, or a boundary at which a condition of a road such as the width of a road, the number of lanes, or the type of surface changes.
Since a navigation device for notifying or emphasizing the classification of roads was not available in the past, the above-mentioned boundary could not be known in advance.
Another problem is that enlarged display is performed for all the intersections. However, enlarged display of an intersection which the user does not want only reduces the useful range of the display screen.
A further problem is that the time for which the enlarged display is made during simulation is sometimes insufficient for the recognition or examination of an intersection, particularly when the vehicle is moving fast.
Thus, intersections which need not be enlarged are also enlarged, and intersections which need to be enlarged for recognition or examination cannot be enlarged for a sufficient time.
Yet another problem of the prior art navigation device is that the cursor on the display must be moved to a desired position to set a starting point or a destination.
For instance, the current position which is detected according to the position information by a GPS (Global Positioning System) receiver is automatically stored as the starting point. However, when the vehicle is not moving, map matching is not effected, and the error in the detection of the current position is substantial, with the result that the position needs to be corrected by manually moving the cursor. Moreover, when the current position is not the starting point, it is necessary to designate the starting position by moving the cursor.
The designation of the destination position by moving the cursor is troublesome particularly for a user who often makes his/her home as the starting point or the destination.
In yet another navigation device disclosed in Japanese Unexamined Patent Publication 5-46090, map information and service information are stored, being divided into a plurality of disks. It has been conceived that these plurality of disks are inserted into a multi-disk reproduction device, and the disk which stores map information about the current position is selected.
However, many disks storing map information of a certain area also store map information of adjacent areas as well, and it sometimes happens that this map information of the adjacent areas is displayed. For example, a disk storing primarily map information of Germany also stores map information of parts of France which are adjacent to Germany. However, this map information of France stored in the disk for Germany is not as detailed as the map information of Germany. For example, express ways are stored, but ordinary roads are not be stored.
It therefore happens with a conventional navigation device, that when a vehicle moves from a German territory to a French territory, a German disk is still reproduced although there is a French disk, with the result that detailed map information or service information cannot be obtained.